Evaluation of site and hydrogeochemistry in an urban groundwater source field

Water demand has increased in metropolitan cities due to fast population growth and industrial development. Jilin City, located in the middle of Jilin province, northeast China, has a population of approximately 4.30 million. The main water source for Jilin City is the Songhua River which has a lot of problems. This study aims to determine the appropriate groundwater resource field for Jilin City by groundwater quantity analysis, groundwater quality analysis and multivariate statistical analysis. Results showed that the groundwater quantity in the study area was separated into four main areas. Most of the study areas had good groundwater supplies. The dominant ions were Ca²⁺, Mg²⁺, Na⁺, NH₄⁺, NO₃⁻, HCO₃⁻ and SO₄²⁻. The groundwater types can be classified as Ca–HCO₃, Ca + Mg–HCO₃, Ca + Na–HCO₃, Ca + HCO₃–SO₄, Ca + Mg–HCO₃ + SO₄ and Ca + Na–HCO₃ + SO₄. The regions of groundwater satisfying the groundwater quality standard can be separated into five main areas. Using principal component analysis (PCA), five principal factors were extracted from the dataset. Factor 1 had high positive loadings for most of the major ions (Na⁺, Ca²⁺, Mg²⁺, HCO₃⁻ and SO₄²⁻) as well as for total hardness (TH) and electrical conductivity (EC), which represents the natural hydro-geochemical evolution of groundwater by groundwater-geological interaction. Factor 2 was dominated by F⁻, pH and PO₄³⁻, which may be due to anthropogenic pollution sources. Factor 3 was dominated by NO₂⁻, NH₄⁺ and NO₃⁻, which may also be due to anthropogenic pollution sources. Factor 4 had a higher loading of chemical oxygen demand (COD), which again may be due to anthropogenic pollution sources. Factor 5 was dominated by Fe and Mn, which are produced by weathering-leaching-dissolution processes. The score values of the principal factors were influenced by urban land use. Chuanying region is the area in which the quality of groundwater is relatively good. It was determined that No. 6 region in Chuanying region is the groundwater resource field which has sufficient good quality water.